Flammable and/or combustible fluids, for example petrol is usually stored in some form of storage tank. A flammable fluid is a liquid that has a flashpoint below 38° Celsius, for example petrol. The flashpoint is the minimum temperature at which a liquid gives off vapour in sufficient concentration to form an air-vapour mixture that can be ignited. A combustible fluid is a liquid that has a flashpoint above 38° Celsius. Combustible fluids include diesel and kerosene.
At retail fuel outlets, for example service or petrol stations for motor vehicles (referred to in some countries as gas or gasoline stations), one or more storage tanks are usually located underground. The underground storage tanks typically have some form of upstanding access pipe provided which leads from the storage tank to ground level. The upstanding access pipe is closed at ground level by some form of lid. In order to determine the amount of fuel, for example petrol, within the storage tank the lid is opened and a measuring stick inserted. The measuring stick extends to the bottom of the tank with the petrol marking the stick to indicate the depth of the petrol within the tank. The problem in determining the amount of stored petrol in this manner is that it is labour intensive and difficult to obtain an accurate measurement. In addition, it is difficult to readily determine from the measurement taken as to whether the storage tank is leaking as such a determination can not be made without first calculating how much fuel has been pumped from the storage tank by customers since the last measurement was taken. For these reasons, all newly constructed petrol stations install some form of automatic measuring system during the construction.
However, in order to install an automatic measuring system to an existing underground storage tank it is often necessary to firstly install an additional upstanding access pipe leading from the storage tank to ground level. This type of upstanding access pipe can also be required for a variety of other reasons, for example to provide an access point to the storage tank for cleaning purposes.
In the past when an upstanding access pipe, otherwise known as a riser, was required for an existing underground storage tank the installation typically involved cold cutting or drilling a series of holes in an exterior surface of the storage tank. Once a suitably sized opening was formed in the storage tank a riser would then be welded to the exterior surface with the riser extending upwardly to ground level. As the petrol within the storage tank is highly flammable installing a riser in this manner is extremely dangerous as a spark or flame created during the installation process could easily ignite the petrol. For this reason the storage tank has to be emptied prior to the installation of a riser to reduce the risk of an explosion occurring. However, an empty storage tank is still potentially explosive as even the slightest amount of residual petrol within an empty storage tank will result in flammable vapour being released into the surrounding air. Accordingly, degassing and the introduction of an inert gas to the empty storage tank was necessary before installation of the riser could safely commence. The process of installing a riser to a storage tank which contains flammable fluid is therefore complex, time consuming and inconvenient.
Accordingly, it would be desirable to provide an apparatus and method for safely forming an opening in a storage tank containing a flammable and/or combustible fluid without having to firstly remove the fluid from the tank.
Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base of the common general knowledge in the relevant art in Australia or any other country on or before the priority date of the claims herein.